ABSTRACT Support is requested for a Keystone Symposia conference entitled Exosomes/Microvesicles: Heterogeneity, Biogenesis, Function, and Therapeutic Developments, organized by Drs. Crislyn D'Souza-Schorey and David Lyden. The conference will be held June 4-8, 2018 at Beaver Run Resort, Colorado. Extracellular vesicles (EVs) have emerged as critical mediators of intercellular communication in both local and distant microenvironments, during normal development and physiological processes, as well as in orchestrating systemic pathophysiological events. EVs comprise a large group of heterogeneous particles, including exosomes and microvesicles, and are released from virtually all cell types. Differing in size, macromolecular composition, and mechanism of formation, subpopulations of extracellular vesicles contain biologically active molecules, such as nucleic acids (DNA, mRNA, microRNA and other noncoding RNAs), proteins (transmembrane receptors, transcription factors, enzymes, extracellular matrix proteins), and lipids that can in part or in sum contribute to the functional capabilities of the vesicle itself, or the reprogramming of target cells that interact with EVs. This complexity presents significant challenges to determining the functional roles of the various EV populations during both normal and pathological processes. Conference sessions will focus on EV cargo and composition; the role of EVs in development; EV-mediated immune regulation; EVs in cancer and metastasis, neurodegeneration and infectious disease; emerging technologies; and harnessing the therapeutic potential of EVs. The overall goal is to deepen our understanding of the structural and functional complexity of extracellular vesicles, their biogenesis and function in health and disease, cargo enrichment, potential as ideal biomarkers, and breakthroughs in their use as therapeutic targets/agents.